INCINERATION WITH ENERGY RECOVERY

INCINERATION WITH ENERGY RECOVERY

INCINERATION WITH ENERGY RECOVERY

Incineration with energy recovery refers to the combustion of waste under controlled conditions to generate electricity and/or heat. The technology produces energy and heat, reduces the volume of municipal solid waste (MSW) that must be handled and destroys harmful substances, provided that the process includes highly advanced air pollution control (APC) equipment. The energy generated is considered to be partially renewable, due to the biogenic (plant-based) content of the waste, such as food and other organic waste, cardboard and wood. The fossil-fuel sourced components of the waste (e.g. plastic materials) are non-renewable. Incineration was often historically applied without energy recovery, but that is increasingly rare given the potential for the technology to be a source of energy in addition to a waste management solution.

Although incineration technology has matured over the last few decades, it is still relatively expensive, and thus primarily used in high-income countries. Incineration has been implemented successfully in jurisdictions with land (or landfill) scarcity, high technical capacity, significant financial resources, strong environmental regulations and typically a low or separated organic waste fraction. It is widely used in Japan where 80% of MSW was combusted in 2015. Around the world, approximately 11% of MSW is combusted, although the technology is most prevalent in high-income countries.

Decision Maker’s Guides for Solid Waste Management Technologies

INCINERATION - THE BASICS

Modern incineration facilities consist of a storage area to sort and store the incoming waste, a crane for lifting the waste from the storage area into the combustion chamber, a heat recovery system that uses the heat from incineration to produce steam in a boiler for electricity generation, an ash handling system to capture non-toxic bottom ash (ash that collects at the bottom of the system), and an APC system, which captures toxic particles that rise with the gaseous emissions (fly ash) and treats harmful gasses prior to release into the air. The operational capacity of incineration facilities

can range from 5 to over 1,000 tonnes per day of MSW; however, most facilities are in the range of 200 to 700 tonnes per day.

The main difference between incineration and open or uncontrolled burning is that the combustion in incineration occurs at a very high temperature in a contained plant which reduces the generation of harmful air pollutants. An incinerator can also capture and utilize heat and steam for electricity. Open burning occurs at a much lower temperature while exposed to the atmosphere.

Incineration Open burning

Control of burning Strict controls on volume and types of waste included as well as temperature of furnace

No control

Energy Recovery Electricity and/or heat potential No potential

Toxic Emissions Pollution

Low due to high temperature combustion, advanced APC equipment and typically strict government emission regulations

Can be 45 times higher than emissions from incineration. They are not captured but rather released into the atmosphere

Comparison of incineration and open burning

WHAT TO KEEP IN MIND WHEN PURSUING INCINERATION

Feedstock requirements: The MSW should contain a sufficient amount of dry, combustible waste (paper, unrecyclable plastics, etc.), and be available at a consistent volume, that varies by less than 20%, to enable effective combustion and a minimum level of electricity and/or heat generation. Waste with a low organics fraction (<50%) is easier for combustion. The feedstock does not need to be homogenous and can include municipal, medical and hazardous waste. Waste that should be avoided includes those with high sulfur or chlorine contents, organic salts, or radioactive materials.

Siting: Assuming multiple sites are available close to the municipality, siting close to industrial plants would benefit both parties by reducing the cost of transportation of waste to the incinerator as well as the distribution cost of electricity and/or heat. If the ash is to be landfilled, siting the facility near a landfill would reduce transportation costs.

Air pollution control: The APC system is a sophisticated and key part of the incineration plant. It ensures that air emissions are kept below harmful levels. The APC system normally comprises a bag filter system in the flue (chimney) to capture the fine particles of the toxic fly ash and also a chemical-based system to capture other harmful gaseous compounds in the flue gas. Emissions are typically monitored continuously for regulatory compliance. Monitoring data is often made publicly available to demonstrate that emissions

are below harmful limits.

Ash disposal: The non-toxic bottom ash normally comprises 10-25% by weight of the MSW processed. It can be treatedand recycled as construction material or used in theproduction of cement. If such use is not possible, it must bedisposed of in a landfill. Toxic fly ash (ranges from 3-5% byweight) is a hazardous material due to an often high contentof heavy metals. It can be disposed of in a hazardous wastelandfill (common in Europe) or can be mixed with bottom ash(common in the US) to be disposed of in a sanitary landfill orused as landfill cover.

Electricity and heat generation: A feedstock with suitable characteristics would generate net electricity of 500-600 kWh/tonne of MSW. In the European Union, it is common for both electricity (500 kWh/tonne) and heat (1000 kWh/tonne) to be generated, with the latter used in providing industrial or district heating. This approach is termed ‘co-generation’.

Public perception: The lingering criticism of local incinerators from the 1960s and ‘70s makes incineration a highly contentious subject among many communities. Decision makers need to include the public in the decision-making process, by providing accurate information, and siting facilities away from residential areas.

Contract duration: Due to the very high capital costs of these plants, contracts for incineration are normally 25-30 years in duration. This is the typical time-period that allows the developer (and its financial backers) to recoup the substantial investment made in the capital equipment. It is important to properly assess possible changes in waste quantities, composition and other related factors over the long term so as to ensure that the municipality is not bound into a contract that prevents waste prevention or discourages recycling or composting initiatives to be developed.

Contractual requirements for waste quantities and composition: Successful incineration plants require a consistent flow of waste feedstock and a consistent composition, with a calorific value between defined levels. The developer and operator of an incinerator will typically insist on a minimum quantity and composition of waste as part of any waste treatment contract with a municipality. Small waste quantities are likely to make the facility too costly due to the high upfront capital investments. If the agreed quantity and composition of waste is not provided by the municipality then the incinerator operator will normally apply a financial penalty to compensate for the effect that the lower quantity or change in composition will have on the plant’s operation.


Notes:Scrubbers and particulate removal systems remove contaminants from the air/gas streams, which helps produce cleaner outputs.

Incineration

Process flow diagram

Grabber collects waste Ash and materials

Steam Generator

Chimney

Scrubber

Particulate removal system

Incinerator

Electricity

Technology overview Incineration (i.e. mass burn) is one of the most common forms of thermal waste treatment technology. It involves the combustion of waste materials in a chamber that contains excess air. There are two main types of inciner-ators: moving grate incinerators and fluidized bed incinerators. In a moving grate incinerator, waste is combusted at temperatures between 1,000°C - 1,300°C as it moves through the furnace by a mechanically driven grate. Waste is successively feed to the combustion chamber on one end and the solid residues are discharged at the other end. In a fluidized bed incin-erator, the bottom of the combustion system is lined with sand (granulars). Heated air is then bubbled through the sand bed and mixes with the waste to achieve a good burnout.

Ideal calorific value of waste (MJ/kg) 6 – 20

Range of waste throughput (tonnes/day) 70 – 1,800

Feedstock(s) Mixed municipal solid waste (MSW), pre-treated MSW

Land requirement (m2/tonnes per year) 0.05 – 0.1

Costs (US$/tonnes per year)

Capex 500 – 890

Opex 50 – 110

Schematic diagram of incineration facility


Informal waste pickers: the contractual requirements of an incinerator-based waste treatment contract could result in pressure to collect as much waste as possible for delivery to the incinerator. In cities where there are major waste picking activities, waste pickers and informal recyclers may lose access to waste materials, their main source of income. It is essential to consider the issues carefully before engaging in an incinerator-based waste treatment contract. A social assessment must be done with measures in place to mitigate these risks. Policies could be developed as part of

an integrated waste management strategy to integrate waste pickers as part of the new system.

Integrated solid waste policy: An incineration facility should be planned as part of an integrated, long-term strategy that also considers waste prevention, reuse, and recycling and composting activities. Recycling and incineration can complement each other if there is sufficient waste volume and the interactions between different initiatives are assessed in detail.

HOW MUCH WILL AN INCINERATION FACILITY COST?

• Costs vary by facility according to the combustion tech-nology chosen since each has unique design character-istics, variations in equipment costs, capacity, site-specificwaste characteristics, space requirements, and regulatoryrequirements.

• On a per tonne basis, capital costs for incineration plantsrange from US$190-1000 per annual tonne, while operat-ing costs range from US$12-55/tonne. This makes inciner-ation generally more expensive than landfilling, compost-ing, and anaerobic digestion, but cheaper than pyrolysisand gasification.

• Below are a few examples of operational expendituresand capital expenditures for incineration facilities (pertonne of waste processed):

Incineration DigestionCapital Expenditures (1) (US$/annual tonne) (2)

Operational Expenditures (3) (US$/tonne) (4)

Europe $600-1000 $25-30United States $600-830 $44-55

China $190-400 $12-22

(1) In Europe and US, predominantly mass-burn/moving grate technologyis used for waste incinerator with energy recovery (waste-to-energy). InChina many incinerators use circulating fluidized bed (CFB) technologywhich reflects the lower end of investment cost although moving grateincinerators are also becoming more common.

(2) Annual tonne is the capital cost of the facility divided by the annualprocessing capacity of the facility

(3) Operating costs without accounting for revenues range between$100-200/tonne. The figures presented in the table are typical operatingcosts (net gate fees) taking into account revenues for electricity and/or heat sales and other revenues. In the EU, also including subsidies toenergy from waste in some countries, these revenues are typically about$100/tonne, hence the resulting operating costs. In US feed-in tariffs forelectricity are typically lower, below $50/MWh.

(4) Mixed waste in the US and the EU is relatively low in organics andwater content and hence high in calorific value. As a consequence, oper-

ating costs for waste with high organics often seen in lower income coun-tries could substantially increase operating costs due to lower revenues

• The high costs of incineration facilities can be heavily off-set by revenues earned from operations, as long as thefacilities are operated at full processing capacity and op-timized technically.

• APC equipment costs are roughly equal to that of the restof the facility. Thus, the costs and importance of APC tech-nology should be clearly understood.

• There are significant potential economies of scale for in-cineration, especially when the cost of APC equipment isfactored in. Hence, if there is sufficient demand for wastetreatment or if a plant can serve a whole region, there maybe a clear financial benefit.

• In general, maintenance and other consumable costs areestimated to be 3% and 1%, respectively, of capital costs.

Capital Costs

• Land and buildingsacquisitions

• Design and construction of thefacility and related systems (steam turbine, APC, etc.)

• Environmental and socialimpact assessments

• Approvals andlicensing

• Machinery andequipment

• Training andmonitoring equipmentREVENUE OPPORTUNITY

Revenues can be obtained from tipping fees, sale of electricity, metals recovery, and carbon finance.


HOW TO RECOVER COSTS OF IMPLEMENTING THESE TECHNOLOGIES

Think in total system terms: Incineration reduces the volume of the waste, elongating your landfill life and often creating a new revenue source for your program. The average lifespan of incineration facilities is about 25 years.

Tipping fees: A major source of income at an incineration facility is tipping fees, which is the fee charged to waste haulers or the municipality per ton of waste brought to the facility. This can offset capital and operating costs. Larger facilities would have slightly lower tipping fees due to small economies of scale.

Sale of electricity and/or heat generated: The electricity and/or heat generated that is not used in running the facility itself could be sold to nearby industries, to the electric grid, or to district heating systems.

4 Assuming 5-year average conversion rate of 1.5139 USD per British pound and 1.18 USD per Euro

Costs are sometimes also calculated based on the per kilo-watt genera-tion electricity from the facility. Comparative costs of thermal treatment options are shown below ($/kW for a 15 MW output)

Incineration with energy recovery $7,000-10,000

Gasification (conventional) $7,500-11,000

Gasification (plasma arc) $8,000-11,500

Pyrolysis $8,000-11,500


Generation efficiency: Incinerators that generate both heat and electricity are significant more energy-efficient (in terms of the using the energy context of the waste feedstock) than those that generate electricity only. Generating electricity is a common challenge and should not be solely relied on. Locating an incinerator adjacent to, or as part of, an industrial facility/area that can use the heat is an effective way of maximizing the use of the available energy. Alternatively, a district heating system can be developed in conjunction with an incinerator.

Preferred tariffs for renewable energy: Governments may provide incentives in the form of tax credits, preferential pricing, discounts, or other benefits to encourage electricity from renewable sources. In the US and Europe, incineration is considered to be a renewable source of energy because the major portion of carbon in the waste does not increase the total amount of atmospheric carbon

Carbon finance: Incineration facilities can be possible candidates for carbon finance where “credits” from the reduction of emissions of greenhouse gases can be sold to offset costs. Incineration facilities prevent the generation of methane in landfills that could have occurred, and generate electricity and/or heat that might otherwise have been generated from fossil fuels.

Materials recovery: The separation of recyclables, particularly high-value metals, prior to combustion can be a significant source of revenue for incineration facilities.

WHERE IS INCINERATION BEING USED AND WHAT HAVE WE LEARNED?

Incineration facilities have been successful in places like Japan and the European Union where space for landfilling is diminishing and the costs of landfilling are increasing. Other factors that have driven the growth of incineration include improved pollution and emissions controls, legally-binding regulations mandating energy generation from renewable sources, targets for reduction in greenhouse gas emissions, and eligibility for carbon credits and other financial and tax incentives. Decision makers and incineration operators have succeeded in gaining public acceptance by including incineration as a key part of their environmental and waste strategies, encouraging recycling, and using waste as a source of energy.

Incineration has been challenged in some low and middle-income countries where facilities built decades ago without proper waste characterization studies and lack of air pollution control equipment resulted in insufficient and low-quality feedstock, inefficient incineration, and high levels of air pollution. The facilities were not profitable due to lack of revenue generation from electricity, and instead resulted in strong public opposition to the technology due to the resulting high costs and pollution.

CLIMATE CONSIDERATIONS:

• Combusting one ton of waste in an incinerationplant prevents one ton of CO2e from being emittedthrough alternative waste treatment methods

• Incineration offsets fossil fuels by generatingsustainable energy


MAYOR’S CORNER: QUESTIONS TO ASK YOUR SOLID WASTE MANAGER OR VENDOR WHO WANT TO CONSTRUCT AND OPERATE THE INCINERATION FACILITY

1. Is the technology appropriate given the local waste composition (organics should be <50%),quantity generated, and seasonal variation? What are the waste generation projections overthe next 20-30 years? Does the size of the proposed incineration facility make sense given theavailability of the feedstock?

2. What systems are in place to ensure the quality as well as a guaranteed supply of the feedstock?

3. Is it financially sustainable? What will the tipping cost be and what cost recovery mechanismswill be put in place?

4. Is there a market for the sale of electricity and/or heat generated from the incineration facility?Is there preferential pricing for waste-derived electricity? Can the incinerator be developed inconjunction with an industrial or residential development or be connected to a grid that can usethe electricity and heat?

5. Can land for the facility be readily obtained? What are the siting requirements for such a facilityand have they been met? Have relevant site studies been conducted to make sure the facilitywill meet local and national regulations?

6. How many local jobs will the facility create?

7. What training and maintenance will be provided over the life of the facility by the private devel-oper? How can local capacity be fostered over time?

8. Does the project developer have prior experience in undertaking complex technical and finan-cial projects with sufficient technical knowledge?

9. Does the technology provider already have an existing facility in operation, operating at a sim-ilar scale, with a similar feedstock? Can the vendor provide operational and performance data,including emissions and costs, for at least several months, if not longer, of continuous operation?

10. Does the vendor have proof of adhering to the local standards set by solid waste and air pollu-tion regulations?

11. What opportunities exist to put the physical by-products of incineration (e.g., bottom ash) toproductive use, such as in road construction or as a component of cement?

References

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INCINERATION WITH ENERGY RECOVERY